Condensed Statements of Patronage Capital and Membership Fees and Accumulated Other Comprehensive Margin (Deficit) (Equity) (USD $) In Thousands	Total	Patronage Capital and Membership Fees	Accumulated Other Comprehensive Margin (Deficit)	Comprehensive Income
Balance at Dec. 31, 2009	$ 560,966	$ 562,219	$ (1,253)
Components of comprehensive margin:
Net margin	22,004	22,004		22,004
Unrealized gain on available-for-sale securities	1,033		1,033	1,033
Total comprehensive margin	23,037			23,037
Balance at Jun. 30, 2010	584,003	584,223	(220)
Balance at Dec. 31, 2010	595,483	595,952	(469)
Components of comprehensive margin:
Net margin	28,828	28,828		28,828
Unrealized gain on available-for-sale securities	592		592	592
Total comprehensive margin	29,420			29,420
Balance at Jun. 30, 2011	$ 624,903	$ 624,780	$ 123